Magnetizers for pigging tools

1. An axial magnetizer module for a smart pig, comprising:

a central shaft; and

at least one magnet bar, coupled to the central shaft by a means for collapsing, and inducing a magnetic field coaxially to a longitudinal axis of the central shaft, the at least one magnet bar comprising:

a first magnet of a first polarity circumferentially disposed around a front end of the central shaft;

a second magnet of a second polarity circumferentially disposed around a rear end of the central shaft;

a front magnetic circuit pole coupled to the first magnet and extending radially outward from the central shaft and configured to induce the magnetic field to the pipe wall;

a rear magnetic circuit pole coupled to the second magnet and extending radially outward from the central shaft and configured to induce the magnetic field to the pipe wall; and

a sensor head to monitor magnetic flux comprising at least one sensor disposed between the front magnetic circuit pole and rear magnetic circuit pole;

wherein the front magnetic circuit pole and the rear magnetic circuit pole include a plurality of wear pads configured to contact the inner diameter of a pipe.

2. The axial magnetizer module of claim 1 , wherein the means for collapsing comprises a torsion spring to allow the magnet bar to move radially inward toward the central shaft.

3. The axial magnetizer module of claim 1 , wherein the first magnet and second magnet are rare-earth permanent magnets; electromagnets; or neodymium-based magnets.

4. The axial magnetizer module of claim 1 , wherein the at least one sensor includes one or more of: a Hall-effect sensor and an ultrasonic sensor.

5. The axial magnetizer module of claim 4 , comprising six magnet bars and forty Hall-effect sensors.

6. The axial magnetizer module of claim 1 , wherein the sensor head has a sloping trapezoid, rhomboid, rectangle, or parallelogram shape.

7. The axial magnetizer module of claim 1 , wherein the sensor head further comprises a suspension system comprising at least one conical spring to position the sensor head during operation.

8. The axial magnetizer module of claim 1 , further comprising a magnet shield to focus the induced magnetic field.

9. The axial magnetizer module of claim 1 , further comprising a joint extending axially from the central shaft to link an additional module of the smart pig.

10. A magnetizer module for a smart pig, comprising:

a central shaft; and

at least one magnet bar, coupled to the central shaft at one end by a collapsing system comprising a link and a torsion spring, coupled to the central shaft at an opposing end by a polyurethane ring disposed circumferentially around the central shaft, and configured to induce a persistent magnetic field coaxially with a longitudinal axis of the central shaft to a pipe wall, the at least one magnet bar comprising:

a first magnet of a first polarity disposed on a front end of the magnet bar;

a second magnet of a second polarity opposite the first polarity disposed on a rear end of the magnet bar;

a front magnetic circuit pole coupled to the first magnet and extending radially outward from the magnet bar;

a rear magnetic circuit pole coupled to the second magnet and extending radially outward from the magnet bar; and

a sensor head comprising at least one sensor configured to measure magnetic flux, the at least one sensor disposed between the front magnetic circuit pole and rear magnetic circuit pole;

wherein the front magnetic circuit pole and the rear magnetic circuit pole are configured to induce the magnetic field to the pipe wall;

wherein the front magnetic circuit pole and the rear magnetic circuit pole include a plurality of wear pads configured to contact the inner diameter of a pipe.

11. The magnetizer of claim 10 , wherein the collapsing system and polyurethane ring are configured to allow the magnet bar to collapse toward the central shaft by up to 25% of the outside diameter of a pipeline.

12. The magnetizer of claim 11 , wherein the magnetizer is sized to navigate pipeline bends of 1.5 times the diameter of the pipeline.

13. The magnetizer of claim 10 , wherein each magnet bar is configured to cover about 30 degrees of the pipe wall.

14. The magnetizer of claim 10 , comprising six magnet bars disposed circumferentially about the central shaft.

15. A smart pig, comprising:

two axial magnetizers, each axial magnetizer comprising:

a central shaft; and

six magnet bars, each magnet bar (a) coupled to the central shaft at one end by a collapsing system comprising a link and a torsion spring, (b) coupled to the central shaft at an opposing end by a polyurethane ring disposed circumferentially around the central shaft, and (c) configured to induce a persistent magnetic field coaxially with a longitudinal axis of the central shaft to a pipe wall, each magnet bar comprising:

a first magnet of a first polarity disposed on a front end of the magnet bar;

a second magnet of a second polarity opposite the first polarity disposed on a rear end of the magnet bar;

a front magnetic circuit pole coupled to the first magnet and extending radially outward from the magnet bar;

a rear magnetic circuit pole coupled to the second magnet and extending radially outward from the magnet bar; and

a sensor head comprising at least one sensor configured to measure magnetic flux, the at least one sensor disposed between the front magnetic circuit pole and rear magnetic circuit pole;

wherein the front magnetic circuit pole and the rear magnetic circuit pole are configured to induce the magnetic field to the pipe wall;

wherein the front magnetic circuit pole and the rear magnetic circuit pole include a plurality of wear pads configured to contact the inner diameter of a pipe; and

wherein the axial magnetizers are positioned relative to each other such that magnet bars cover the entire pipe wall.